1. Field of the Invention
The present invention relates to a device to remove electrostatic charges from a body, of a type comprising at least one grounding conductor operatively interconnected between said body and a grounding line.
More particularly, in the embodiment to which reference is made in the progress of the present description, the device in question is especially conceived for use in electrostatic painting plants, in order to eliminate the electrostatic charges inevitably tending to store up in the articles being manufactured and/or in the different apparatus and structures forming said plants. However the principles proposed by the present invention can, after suitable adaptations if necessary, be validly utilized to remove electrostatic charges from machines or machine parts of other kinds, such as for example, photocopying machines, electric motors and the like, and/or on the occurrence of any other situation in which electrostatic charges stored in excess in a body are wished to be reduced or eliminated.
2. Prior Art
It is known that current plants for electrostatic painting of articles of manufacture essentially comprise booths or tunnels in which atomized paint is usually sprayed onto the article of manufacture by appropriate equipment usually consisting of suitable guns fed with a compressed air flow carrying the paint particles. Disposed close to the gun delivery nozzle is one or more electrodes creating an electric field adapted to electrostatically charge the paint particles so that they can be attracted by and adhere to the article.
A subsequent baking step causes polymerization of the paint and final adhesion of same to the article being manufactured.
It is pointed out however that electrostatic, magnetic, electromagnetic currents and/or currents of any other, and in any case undesired, nature produced for electrostatically charging the paint particles, adversely affect a correct painting process at the moment that the article of manufacture and/or given parts or fixtures in the painting plant are also electrostatically charged. In more detail, the presence of these electrostatic charges in excess can for example give rise to repulsion of the arriving paint particles by the electrostatically charged article, loss of the electrostatic charge induced in the paint particles while they are moving towards the article, and production, under particular circumstances, of electric discharges between the electrodes associated with the gun delivery nozzle.
Such problems bring about a bad operation of the plant in general, which will impair both the quality efficiency, in terms of evenness and homogeneity of the paint layer coated onto the article of manufacture, and the quantity efficiency intended as the ratio in percentage terms between the paint amount deposited onto the article and the paint amount delivered by the nozzle. In plants of normal conception the quantity yield in many cases does not exceed values in the range of 50-60%.
It is pointed out that the high percentage of dispersed material also has adverse effects on the sanitary work conditions and the environment in general, which makes it necessary to adopt many measures of expensive application in order to comply with the severe anti-pollution provisions regulating painting and similar activities involving the use of chemicals.
In addition, since paint encounters many difficulties in adhering to the article of manufacture due to the presence of electrostatic charges thereon, careful checks are necessary while painting is being carried out, and subsequent interventions are needed in order to retouch those parts of the article on which there was an insufficient amount of deposited paint, which will bring about a slowing down in the production cycle and an increase in the production costs.
In order to limit the problem resulting from the excessive presence of electrostatic charges, recent studies being the object of the European Patent application No. 0 572 358 have suggested to mix an additional fluid with the air delivered from the gun nozzle, in the presence of which fluid the effect of the electrostatic charge induced on the paint particles is increased so that said particles will adhere more strongly to the article of manufacture.
This expedient has brought to important improvements with reference to the painting efficiency and the working quality. However, all problems connected with an insufficient drawing off or "draining" of the electrostatic charges from the article of manufacture and/or the different plant parts remain substantially unchanged.